Treating tin-scrap.



UNITED sTATns PATENT OFFICE,

Specification of Letters Patent.

Application led October 19, 1904i. SerialNo. 229,071.

To a/ZZ whom, t may concern:

Beitknown that I, MEREDITH' LEITOH, a citizen of the United States, residing at Brooklyn, Kings county, New York, have invented certain new and useful Improvements in Treating Tin-Scrap, of which the following is a full, clear, and exact description.

My invention relates to improvements in treating tin-scrap, by which I mean tin cuttings, old tin cans, and the like, so as to recover the tin from the same in an economical and eliicient manner.

Heretofore tin-scrap has been subjected to electrolytic action ina suitable electrolyte,

such as caustic soda, and the tin in that way removed from the cans and deposited on suitable cathodes.

It has been the practice to subject tin-scrap made up of trimmings to the action of the electrolyte without any previous treatment. In the case of tin cans and the like it has been the practice to puncture or cut out the cans, so that the electrolyte can circulate through them freely, and in some cases to remove the labels by washing. Both of these steps in the preparation of the cans for' the electrolytic bath are slow and expensive and, while entailing eXtra expense, are quite unsatisfactory in their results. principal difficulty is that even after the cans are washed as thoroughly as they can be by any commercial washing process some paste, oil, grease, and vegetable matter adheres to them, while in the case of trimmings the palmoil which is applied to the tin as it leaves the tinning-bath. adheres. These substances ladhering to the tin are known in the art as lth,which is the bane of electrolytic processes, since it interferes with the action of the electrolyte. When caustic soda is used, the oil and grease combine with it to make soap, while the vegetable matter is attacked by it and causes it to deteriorate so as to soon be unsuitable for use. The problem therefore is how to remove the filth or change it into some form which will not interfere with the electrolyte and to do thiseconomically and .satisfactorily without destroying thev tin which it is desired to save. I have discovered The and in carbonizing the remainder by subjectdized atmosphere.

A further improvement consists in agitat- -ing the cans in such a manner as to dislodge much, if not all, of the carbonized `material, and thereby separate it from the scrap before the scrap is subjected to the electrolyte. The treatment of the tin cans in the absence of oxygen preserves the tin, which otherwise would be lost.

The process, in addition to the advantageous results above specified, also has the advantage in that in some forms of apparatus for carrying out my improvements the solder can simultaneously be practically all removed Patented sept. 26, 1905 ing it to a carbonizing temperature in a deoXifrom the tin cans so that it does notinterfere with the detinning and is not present to lower the grade of iron of castings made from'scrap after the detinning process is completed.,l

Furthermore, the solder itself which is removed is valuable and is thereby separated so that it also can be saved. The solder collected more than pays for the cost of carrying out the step which constitutes my present improvement. My invention, however, is not necessarily allied to desoldering, since it can be carried out by mechanism which does not desolder. When it is carried out in a desoldering mechanism, however, it has the advantage of not only converting the filth into an inert substance, but also the advantage of opening up the cans by separating the parts thereof so that the electrolyte can circulate freely through the scrap.

The following is a description of my invention, reference being had to the accompanying drawings, in which- Figure l is a longitudinal section of the preferred form of apparatus adapted to be used in carrying out my invention. Fig. 2 is a plan view of the same. Fig. 3 is a diagram.

Referring more particularly to the drawings, thevapparatus to the left represents a centrifugal carbonizing and desoldering fur- `nace, and the apparatus to the right repre-- sents a detinning-bath. In vthe furnace, A represents an inclosing wall provided with a door B, through which material can be removed from below. Within the chamber formed by the wall A is a revolving basket or centrifugal separator 'D, preferably of' steel, mounted upon the shaft E, which shaft is supported in bearings F F and driven by .the pulley G. This basket D is provided with IOO IIO

elongated perforations CZ in its sides for the purpose hereinafter described. The bearings F F are of any well-known type suitable for use in connection with a heated shaft. Within the basket D extends a hopper H, preferably conical inform, as shown. This hopper forms a cover for the chamber formed by the wall A, being supported at the upper end of said wall, se as to seal the upper partof the chamber. The hopper is provided with spiral ribs I, which coact with teeth J on the revolving sleeve surrounding the shaft E in such Way as to assist in forcing the material within the hopper downward into the basket D. The upper part of the chamber formed by the wall A and the hopper H is provided with an outlet K, the lower end of which dips into the tank L so as to be sealed by the electrolyte therein. The upper edge of the basket D is provided with a horizontal ange D, which extends over a horizontal iiange D2, carried by the wall A, so as to substantially prevent matter rising above the edge of the basket from passing between the upright wall of the basket and the wall A. The pipe M eX- tends through the wall A and into the basket D, where it is provided with orifices m. Through this pipe is supplied a mixture of gas and air by pipes N and O. respectively, said pipes being provided with stop-cocks a and 0 for controlling the supply of gas and air in such a way that the proportions shall be those necessary for the burning of the gas within the furnace without the leaving of any free oxygen.

At any convenient point or points on the circumference of the furnace I provide a feeding and disintegrating mechanism which assists in causing the cans or other matter within the basket D to be fed upward along its sides, so as to be discharged through the discharge-opening K, and also tends to knock the cans into pieces and to jar off earbonized material therefrom. This consists of a series of toothed disks P, mounted on a shaft Q, journaled at R and R and inclosed by the coverl ing S. The teeth upon these disks protrude through the elongated orifices d in the basket D, so that rotation of the basket produces rotation of the disks. If the shaft Q is exactly vertical, the only action of these disks is to hit the cans as they engage with the teeth, and thus jar them so as to cause the parts to separate and to remove the solder and more or less of the carbonized material thereon. In practice, however, the shaftQ, is inclined slightly in the direction opposite to the direction of rotation of the basket D, from which it results that the blows which the scrap within the basket D receive are in an upward direction and cause the scrap to move slowly upward along the sides of the basket D until discharged through the opening K. The angle of inclination of the shaft Q is preferably so slight that it cannot be shown in the drawings.

The disks B are, in effect, geared with the basket D and are rotated thereby on account of that engagement.

Fig. 3 shows the relation of the axis of the shaft Q to the axis of the shaft E, as would be seen in looking from the periphery at the left toward the center of the machine. The size of the angle 1s greatly exaggerated. ln

this figure, Q represents the axis of the shaft Q, and E represents the axis of the shaft E with its inclination exaggerated. The arrow represents the direction of rotation of the basket A in the apparatus of Figs. l and 2.

The tank L is of iron and forms the anode of the battery T, the cathode being the iron plates U, suspended from the bus-bar V. The liquid in this instance is caustic soda. The cans falling to the bottom of the tank are thus electrically connected to the anode andare acted upon electrolytically, the tin being deposited on the cathode U. l have not shown any means for distributing the cans in the tank L or removing them therefrom, since any proper means known to the art can be used for that purpose.

In carrying out my method with the apparatus above described l first feed the cans into the hopper H, meanwhile revolving the basket D by means of power applied to the pulley (i, the gas and air mixture being supplied and ignited, so as to raise the temperature within the furnace to that required for earbonizing, and preferably to that required for melting the solder in the cans. The revolution of the basket, together with the sleeve connected thereto bearing the pins J, feeds the cans in the hopper downward into the basket l), where they are subjected to the action of heat and centrifugal force, with the result that as soon as the solder is melted it is thrown oil' by centrifugal force through the perforatious (Z in the sides of the basket D, the sharp blows which the cans receive from the disks l) aiding in the dislodgment of the solder and carbonized matter and also the disintegration of the cans. The solder is discharged by centrifugal force through the openings d, and the earbonized matter which has been dislodged also sifts through those openings and falls beneath the basket D, from which both solder and carbonized material are removed as necessary through the door B. '.lhe cans which are fedinto the hopper H beingpressed downward, together with the feeding-disks l), cause the desoldered cans, which are in the basket D, to move upward until they pass above the iiange D', at which time the centrifugal force throws them outward to the exit K, provided for that purpose, by which they are conducted into the tank L. As above stated, the liquid in the tank L acts to prevent the egress of the products of combustion through the discharge-opening K, so that they can find exit only through the opening in the hopper H and in passing out through lOO this opening constitute a gas seal therefor and prevent the ingress of air at that point. The atmosphere 4within the furnace i's therefore entirely deoxidized, and no oxidation of the material treated takes place within the furnace. The carbonaceous matters are thoroughly carbonized and the solder is removed.

The tin coating is subsequently removed by- In the treatment of tin-scrap matter madeup of trimmings by my process the volatile portion of the palm-oil which is ordinarily applied to the tin in its manufacture is driven off and the remaining carbonaceous matter carbonized, so that my improvement constitutes a marked advantage in the process of recovering tin from scrap of that kind, asY

well as from old cans and the like..

In case it is not desirable to detin the cans immediately after their discharge from the carboniZing-furnace the tank L can be filled with water, which acts to seal the discharge K. The cans may then be removed as desired'and subjected to the detinning-bath at such time or place as may be convenient.

The mechanical features of the furnace shown and described herein are claimed in my copending application, Serial No'. 232,420, filed November 12, 1904.

What I claim isv Y 1. In the treatment of tin-scrap forthe recovery of tin by a detinning-bath the improvement which consists in converting the filth adhering to said scrap into a form not detrimental to the bath without removing the coating of tin and keeping the medium surrounding the scrap While being thus treated inert relatively to the tin thereon.

2. In the treatment of tin-scrap for the recovery of tin by adetinning-bath the improvement which consists in volatilizing the volatile portions of the filth and carbonizing the carbonaceous matter of the filth and meanwhile keeping the medium surrounding the scrap deoXidiZed and at a temperature suliiciently high to carbonize the carbonaceous Ward and to become disintegrated.v

matters but not high enough to remove the coating of tin from the scrap.

3. In the treatment of tin scrap for the recovery of tin by a detinning-bath the improvement which consists in volatilizing the volatile portions of the lth and carbonizing the carbonaceous matters of the filth in a deoxidized atmosphere heated sufficiently to carbonize the carbonaceous matters but not to remove the tin coating from the scrap and jarring said scrap so as to remove the carbonized matter therefrom.

4.. In the process of treating tin-scrap comprising old tin cans for the recovery of tin by a detinning-bath the improvement which consists in volatilizing the volatile portions of the filth and carbonizing the carbonaceous matter o f the filth in a heated deoxidized atmosphere without removingv the tin coating and subjecting the cans While in said heated atmosphere to mechanical blows and thereby disintegrating them.

5. In the process of treating tin-scrap consisting of old tin cans, the improvement which consists in subjecting the same to heat in a. deoxidized atmosphere and subjecting the cans thus heated to mechanical blows.

6. In the process of treating tin-scrap consisting of old cans, the improvement which consists in subjecting the same to heat in a deoxidized atmosphere and periodically striking the cans thus heated and thereby disintegrating them and impelling them in an onward direction.

7. In the process of treating tin-scrap consisting of old cans, the improvement which consists in subjecting the same to heat in a deoxidized atmosphere and striking the cans thus heated with blows in an obliquely on- 95 ward direction and impelling them onward by such blows.

' 8. In the process of treating tin-scrap consisting of old cans, the improvement which consists in subjecting the same to heat in a IO deoxidized atmosphere and simultaneously subjecting them to centrifugal force and striking them with blows in an obliquely onward direction thereby causing them to move on- IO Signed at New York city, New York, this 18th day of October, 1904.

MEREDITH LEITCH.

i Witnesses: i

' SKINNER, L. VREELAND. 

